John McCarthy

LISP of John McCarthy

John McCarthy (1927-2011) is a legendary person in the fields of computer science and AI (artificial intelligence). Primarily known as the creator of one of the longest-lived computer languages in use—LISP (in 1958), McCarthy was one of the first people, been interested in AI (since 1948) and coined the term in 1955. He also developed the concept of timesharing in the late fifties and early sixties. He made also substantial contributions to the theory of computation and knowledge representation.

John McCarthy was born in Boston, Massachusetts, on September 4, 1927, to the immigrant family of John Patrick McCarthy (Irish Catholic) and Ida Glatt-McCarthy (1893-1957) (Lithuanian Jewish).

When the Great Depression started in the beginning of 1930s, McCarthy's parents lost their house, and the family (which now included a second child, Patrick), became briefly peripatetic. They lived for a short while in New York and then in Cleveland, before finally settling in Los Angeles (in part because of John's respiratory problems), where the senior John McCarthy was hired as a labor organizer for the Amalgamated Clothing Workers and developed a hydraulic orange juice squeezer. Ida McCarthy worked as a journalist and had been active in the women's suffrage movement and both parents of John were active members of the US Communist Party.

Like many child prodigies, John McCarthy was partly self-educated. Due to childhood illness (respiratory problems), he began school a year late, but he quickly made up the time on his own, skipped several grades, and wound up graduating from Belmont High School in Los Angeles two years early, in 1943.

John McCarthy as youngAs a teenager McCarthy developed an interest in mathematics and decided he wanted to go to the CalTech—California Institute of Technology. In his application to CalTech he wrote a one-sentence statement of purpose: "I intend to be a professor of mathematics."

Receiving a B.S. in Mathematics in 1948, McCarthy initially continued his graduate studies at Caltech, but in 1949 moved to Princeton University, where he received a Ph.D. in Mathematics in 1951.

McCarthy remained as an instructor at Princeton from 1951 until 1953 when he came to Stanford as an assistant professor. In 1955, he left for Dartmouth and then for MIT before returning to Stanford in 1962 as a full professor of computer science, where he stayed until his retirement almost 40 years later.

McCarthy's idea for AI originated in September 1948, when he went to the Hixon Symposium on Cerebral Mechanisms in Behavior, a conference that joined together leading researchers in different areas related to cognitive science, including famous psychologist Karl Lashley, as well as mathematicians Alan Turing and Claude Shannon. As McCarthy listened to the discussions comparing computers and the brain, he had a watershed moment. From that time on, his chief interests related to the development of machines that could think like people.

In 1950s, McCarthy was not the only researcher, dabbling in what would be called artificial intelligence. There were several scientists (including Marvin Minsky, Herbert Simon, Allen Newell and Oliver Selfridge) working in this field. What distinguished McCarthy's work was his emphasis on using mathematical logic both as a language for representing the knowledge that an intelligent machine should have, and as a means for reasoning with that knowledge. This emphasis on mathematical logic was to lead to the development of the logicist approach to artificial intelligence, as well as to the development of the computer language LISP in 1958.

The other difference between McCarthy's approach to AI and others, was that previous work in AI had focused on getting a computer to replicate activities that are challenging for humans, such as playing chess and proving theorems of mathematics. In contrast, McCarthy was concerned with mundane and seemingly trivial tasks, such as constructing a plan to get to the airport.

McCarthy maintained that there were aspects of the human mind that could be described precisely enough to be replicated: "The speeds and memory capacities of present computers may be insufficient to simulate many of the higher functions of the human brain," he wrote in 1955, "but the major obstacle is not lack of machine capacity but our inability to write programs taking full advantage of what we have."

The term "artificial intelligence" was proposed by McCarthy in 1955, when he began writing (with Minsky, Shannon, and Nathaniel Rochester), the proposal to fund the first conference dedicated to the topic—the famous Dartmouth conference on artificial intelligence, which took place in the summer of 1956.

In 1961, McCarthy was the first to publicly suggest that computer timesharing technology might lead to a future in which computing power and even specific applications could be sold through the utility business model (just like water or electricity). He claimed that "computing may some day be organized as a public utility". This idea of a computer or information utility became very popular in the late 1960s, but faded by the mid-1990s. In the beginning of 2000s however, the idea has resurfaced in new forms (cloud services).

A general view of Analytical Engine

McCarthy hosting a chess match in 1966

In 1966, McCarthy hosted a series of four simultaneous computer chess matches carried out via telegraph against rivals in Soviet Union (see the upper photo). Although helped pioneer computer chess, he came to think the game was a distraction for programmers.

During the 1970s McCarthy presented a paper on buying and selling by computer, prophesying what has become known as e-commerce. He also invited a local computer hobby group, the Homebrew Computer Club, to meet at the Stanford. Its members included Steve Jobs and Steven Wozniak, who later would go on to found Apple Inc. However, his own interest in developing time-sharing systems led him to underestimate the potential of personal computers. When the first PCs emerged in the 1970s he dismissed them as "toys".

In 1958, McCarthy specified LISP (name derives from "LISt Processing")—the second-oldest high-level programming language in widespread use today (only Fortran is older, by one year). Like Fortran, Lisp has changed a great deal since its early days, and a number of dialects have existed over its history. Today, the most widely known general-purpose Lisp dialects are Common Lisp, Scheme, and Clojure.

Linked lists are one of LISP languages' major data structures, and its source code is itself made up of lists.

Originally created as a practical mathematical notation for computer programs, LISP is based on the notation of Alonzo Church's lambda calculus. It quickly became the favored programming language for AI research. As one of the earliest programming languages, Lisp pioneered many ideas in computer science, including tree data structures, automatic storage management, dynamic typing, and the self-hosting compiler.

In 1982 McCarthy appears to have originated the idea of the space fountain, a form of "space elevator", a tremendously tall tower extending up from the ground.

John McCarthy was a holder of many awards, including the Turing Award (1971), the first IJCAI Award for Research Excellence (1985), the Kyoto Prize (1988), the National Medal of Science (1990), and the Benjamin Franklin Medal in Computer and Cognitive Sciences (2003).

John McCarthy married three times. With his first wife, Martha Coyote, he had two daughters. His second wife, Vera Watson (1932-1978), a programmer and mountaineer, the first woman to complete a solo ascent of Aconcagua in South America, died in October, 1978, attempting to scale Annapurna, Nepal. He was survived by his third wife, Carolyn Talcott and their son.

John McCarthy died on October 24, 2011, in Palo Alto, CA, of heart failure.